1. Field of the Invention
The present invention relates to an apparatus for noninvasively monitoring changes in the heart contractions of the heart by use of electrocardiogram information and pulse wave information.
2. Related Art
The non-invasive monitoring apparatus uses mainly the information of electrocardiograms, arterial oxygen saturation, blood pressure measured by the oscillometric blood-pressure measuring apparatus and the like as parameters representative of dynamic states of a patient. Of those parameters, electrocardiogram information, arterial oxygen saturation and the like may continuously be measured. In particular the electrocardiogram information is used as a parameter sensitively representing a change of a dynamic state of the patient.
Thus, the electrocardiogram information has been used as the continuously monitoring parameter. An arrhythmia of the patient is monitored by use of the waveforms and heart rates on the electrocardiogram. The monitoring based on only the electrocardiogram has the following problems.
The patient monitoring apparatus can monitor an abnormality, e.g., arrhythmia, of the excitation conducting system, but cannot monitor, for example, a pulse deficit, which arises from an abnormality of the heart contraction. In the case of the pulse deficit, the heart cannot supply sufficient amounts of blood to the peripheries of the internal organs, to possibly cause serious diseases. For this reason, it is necessary to monitor the occurrence of the pulse deficit in a continuous manner. Here, the term "pulse deficit" includes two states, a first state in which the heart propels little amount of blood and a second state in which the ventricle is insufficiently filled with blood and the heart contraction is unsatisfactory.
Where only the electrocardiogram information for the parameter continuously and non-invasively obtained is used, there is a limit in monitoring changes in the heart contractions.